1. Field of the Invention
The present invention relates to an image forming apparatus (e.g., a laser printer) and to a developer cartridge removably mountable to the image forming apparatus.
2. Description of the Related Art
Conventionally known laser printer in which a developer cartridge is removably mountable containing a toner can detect whether or not the developer cartridge is mounted, and the mounted developer cartridge is new.
For example, a cartridge that is provided with a detecting means including an encoder for detecting the rotation speed of an agitation shaft in the toner cartridge, a transmission type photosensor, and a lever member which acts after a predetermined time when a new toner cartridge is mounted is proposed. The lever member is designed so that, after the rotation of the motor, when a pulse is not detected immediately but detected after a predetermined time from the transmission type photosensor, the mounted toner cartridge is detected as new. While the pulse is detected immediately after the rotation of the motor, the mounted toner cartridge is detected as used (see Japanese Unexamined Patent Publication No. 2003-316227).